Simulated supercharger control for aircraft engines



Oct. 27, 1959 J. PORT SIMULATED SUPERCHARGER CONTROL FOR AIRCRAFTENGINES Filed Nov. 24', 1954 38 Bud HIV nUTOJINYH un .Si onta Rtu mkukuntkl United States Patent O SllVIULATED SUPERCHARGER CONTROL FOR AIRCRAFT ENGINES Julius Port, Newark, NJ., assignor to Curtiss-Wright Corporation, a corporation of Delaware Application November 24, 1954, Serial No. 470,915

9 Claims. (Cl. 3S--12) -My invention relates to ground based training apparatus for aircraft personnel. More particularly, theinvention relates to apparatus for simulating fluctuations in manifold air pressure occurring in an engine having a dual turbo-supercharger system upon shifting from single turbo-supercharger operation to dual turbo-supercharger system upon shifting from single turbo-supercharger operation or vice versa, and including time delay means of a unique character.

In certain types of aircraft as for example the B-36 (Air Force designation) the reciprocating engines are each provided with a dual turbo-supercharger system to maintain carburetor air inlet pressure at a desired amount during flight operations at high altitudes and sustain the horsepower output of the engine. The system includes a right turbo-supercharger which operates continuously during tlight, and a left turbo-supercharger which is utilized only under cetain conditions to prevent a marked decrease in the efficiency of the turbo-supercharger system, as for example when climbing. The left turbosupercharger operates only in conjunction with the right turbo-supercharger and during such operation turbine speed of the turbo-superchargers is less than when the right turbo-supercharger operates alone. An engineers turbo-supercharger selector switch determines according to its position whether the right turbo-supercharger shall operate alone or in conjunction with the left turbosupercharger.

One of the objects of my invention is to provide means for realistically simulating the effect upon manifold air pressure of a shift from single to dual turbo-supercharger `operation or vice versa on operation of the turbo-supercharger selector switch.

It is another object of my invention to provide appa- `ratus of the described type including time delay circuitry employing but a single timing device for effecting a particular response a predetermined period of time after operating the turbo-supercharger selector switch to either its single or dual turbo-supercharger position.

Other objects and advantages of my invention will be more fully set forth in the following description referring to the accompanying drawings, and the features of novelty will be pointed out with particularity in the claims `annexed to and forming a part of this specification.

Referring to the drawings, Fig. l is a diagrammatic villustration showing apparatus for simulating the effect `upon manifold air pressure of a shift from single to dual zor dual to single turbo-supercharger operation.

Fig. 2 is a graph showing the variation occuring in .manifold air pressure upon shifting from single to dual lturbo-supercharger operation.

In Fig. 1 of the drawings, reference character 1 designates a simulated lever of a turbo-supercharger selector switch which controls contact arm 2 to thereby open and close contacts 2a and 2b. Contacts 2a and 2b are i11- cluded in time delay circuitry comprising the timing relay 3, turbo control relay 4 and associated connections. As ,shown a timing relay 3 includesA the heating element 5 f; ICC

and contact 6a. The contact arm 6 of the timing relay is composed of two metal strips having unequal coefficients of expansion such that the arm moves in position to close the contact 6a when suiicient heat is generated by the heating element 5 a predetermined period of time after its energization. An energizing circuit for element 5 extends from a positive DC. supply voltage -l-E(D.C.) over connection 7, Contact 2a, line 8, element 5, line 9, contact 10b of relay 4, line 11, line 12, and contact 13a to ground provided the contacts 2a, 10b and 13a arel closed. The contact arm 13 is controlled by lever 14 which is normally positioned to maintain contact 13a closed but which may be positioned to open contact 13o as by an instructor to simulate a power failure; Element 5 of relay 3 may also be energized over the circuit extending from the positive voltage source -l-E(D.C.) over connection 15, contact 10a, line 9, element 5, line 8, contact 2b, line 1.6, line 12, and contact 13a to ground provided the contacts 10a and 2b are closed. The turbo control relay 4 may be picked up over a circuit which extends from the supply voltage +E(D.C.) over line 17, the coil of relay 4, line 18, contact 6a, connection 19, line 8, contact 2b, line 16, line 12, and contact 13a to ground provided contacts 6a and 2b are closed. A stick circuit is provided for the turbo control relay 4 extending from voltage source -I-E(D.C.) over line 17, the relay coil, line 20 including the resistor 21, and the contact 22b to ground.

The described time delay circuitry is operated by mov.- ing the lever 1 from an initial position with either con.- tact 2a or 2b closed corresponding respectively to the selection of single or dual turbo-supercharger operation, to the other position to simulate a shift from single to dual or dual to single operation. With lever 1 in the position shown in the drawing and the contact 2a closed corresponding to the selection of single turbo-supercharger operation the turbo control relay 4 is de-energized and contact 6a of the timing relay is open. Assuming that the lever 1 is moved to the left to open contact 2a and close contact 2b an energizing circuit is completed for the heater element 5 extending from the voltage source -l-E(D.C.) over connection 15, contact 10a, line 9, element 5, line 8, Contact 2b, line 16, line 12, and contact 13a to ground. Accordingly, the element 5 heats up and after a 'predetermined period of time Contact 6a closes causing turbo control relay 4 to be picked up over the circuit which extends from the voltage -l-E(D.C.) over line 17, the relay coil, line 18, contact 6a, connection 19, line 8, contact 2b, line 16, line 12, and contact 13a to ground. When the relay 4 picks up contact 10a opens and contacts 10b and 22h close. Contact 22b completes Vthe stick circuit for relay 4 extending from voltage source +E`(D.C.) over line 1'7, the relay coil, line 20 including resistor 21 and Contact 22h to ground. The energizing circuit for the element 5 of timing relay 3 opens at contact 10a whereupon the heating element cools and contact 6a opens to restore the timing relay to its initial or normal condition. lt is now apparent that by moving the simulated lever from the single to the dual position to close the contact 2b, the turbo control relay 4 was picked up at the end of a predetermined period of time, and although the timing relay 3 was operated in the process of effecting the energization of relay 4 such timing relay was nevertheless thereafter restored to an -l-E(D.C.) over connection 7, contact 2a, line 8, element 5, line 9, contact 10b, line 11, line 12, and contact 13a to ground. The element 5 heats up and closes the contact 6a necessarily after the same predetermined period of time as in the example discussed in the immediately preceding paragraph, whereupon turbo control relay 4 drops out, opposite ends thereof being connected with the same potential -I-E(D.C.), one end of the coil being connected to the voltage source -l-E(D.C.) over the line 18, contact 6a, line 8, contact 2a and connection 7, whereas the other end connects thereto over line 17. Contacts 22b and lb open, and contact 10a closes. The resistor 21 limits the flow of current to ground over the contact 22b just prior to its opening. When contact 10a closes it connects one end of element to the voltage source -l-E(D.C.) over line 9, contact a and connection 1S. The other end of element 5 connects with voltage source -i-E(D.C.) over line 8, contact 2a and connection 7. Accordingly the heating element cools off and contact 6a opens to restore the timing relay to the initial condition. The time delay circuitry is unique in that a response, namely the energization and the deenergization of the turbo control relay 4 are effected substantially in the same predetermined period of time after changing the position of the simulated super-charger selector lever with but a single timing device, namely timing relay 3.

It is a well-known property of relays in general, that the operate and release times of a given relay are unequal; this is necessarily true also of relays 3 and 4. However the operate and release times of the relay 4 are, in view of its electro-magnetic actuation, negligibly small compared to those of the relay 3 which is electrothermally operated. In view of the fact that the time delay of the circuitry described is determined substantially solely by the operate time of relay 3 and is substantially independent of its release time, such time delay is substantially the same for the case of switching of selector 1 from its single to its dual position as for the case of its switching in the reverse direction.

It is readily seen that the relay 4 is a bistable circuit means in the sense, that having been previously deener- `gized it is initially energized upon closure of the contact 6a and remains energized even through the contact 6a immediately reopens, and that having been previously energized it is initially deenergized also upon closure of contact 6a and remains deenergized even though again the contact 6a immediately reopens. Stated somewhat differently, closure of the contact 6a operates as a signal to trigger the relay 4 alternately from its stable deenergized state to its stable energized state and vice versa. The relay is capable of remaining in either stable state indefinitely. On the other hand the relay 3 operates in monostable fashion; it has only one stable state, namely that in which the contact arm 6 is in the illustrated position. The contact arm 6 may remain in such stable position indefinitely, but in `every instance of departure therefrom (responsive to energization of relay 3) it will revert thereto on termination of a period which is essentially the sum of the operate and release times of relay 3. The trigger signal will be supplied to relay 4 upon termination of the operate period of relay 3.

Operation of the turbo control relay 4 a pre-determined period of time after moving the turbo supercharger selector lever into a dual or single position determines the operation of a right turbine r.p.m. servo 23 and a left turbine r.p.m. servo '24 which function in conjunction with a manifold air pressure servo 25 to simulate the fiuctuation occurring in manifold air presure upon shifting from single to dual or dual to single turbosupercharger operation. The manifold air pressure servo 25 may be taken as a'n example of other servo systems inthe apparatus including the right and left turbine r.p.m. servos '23 and 24, air fiow servo 26, and r.p.m.

servo 27. Referring to the manifold air pressure system l as typical of each of the other servo systems, such servo includes a servo amplifier 28 to which are applied a number of control voltages which will be hereinafter particularized, a motor 29 responsive to the amplifier output, a feedback generator 30 driven by the motor 29, and a potentiometer 31 having a slider contact 32 which connects through a gear reduction box 33 to the motor generator set. The servo amplifier 28 is a summing amplifier for determining the resultant of the respective input voltages. Such amplifiers are well-known in the art for 'algebraicaliy summing a plurality of A C. voltages of varying magnitude and polarity and a detailed circuit illustration is therefore unnecessary.

As indicated the output of the amplifier 28 controls a motor generator set which is diagrammatically illustrated in the other servo systems of Fig. l as a unit and designated M G. The operation of the motor generator set is essentially the same in each of the various servos and a single illustration for the manifold air pressure servo is therefore suliicient. The motor 29 is of the -two phased type, the control phase 34 of which is energized by the amplifier output as illustrated, the other phase 3S being energized by a constant reference A.C. voltage el dephased 90 from the control voltage. The operation of this type of motor is well-known, rotation being in one direction when the control and reference voltages of the respective phases have the same instantaneous polarity, and in the opposite direction when the instantaneous polarity of the control voltage is reversed with respect to the reference voltage, the rate of rotation in both cases depending on the magnitude of the control voltage. The generator 36 which is driven by motor 29 is a two-phased generator having one phase 36 energized by a 90 dephased A.C. reference voltage e2, the other phase 37 generating according to the motor speed a feedback voltage en, for purposes of velocity control. The motor 29 also serves to operate through gear reduction box 33 and suitable mechanical connections indicated by dotted line 38 the contact 32 of potentiometer card 31 and the manifold air pressure indicating instrument 39.

The potentiometer resistance element 31 may be of the well-known wound card type and is circular or band form in practice, but is diagrammatically illustrated in plane development `of clarity. A structural arrangement Y that may be conveniently used for a servo motor and potentiometer combination of the character above referred to is shown in Patent No. 2,431,749 issued December 2, 1947 to R. B. Grant for Potentiometer Housing and Positioning Structure. It will be apparent that operation of the servo motor in either direction causes the lpotentiometer slider contact to move to a corresponding angular position on the potentiometer element for deriving, i.e., picking-off potentiometer voltages depending on the contact position. The potentiometers of the various servos in the apparatus are shaped or contoured as required so that the value of the derived voltage at the potentiometer 'contact bears a certain relationship to the linear movement of the slider contact depending upon the particular function of the potentiometer, and has an A.C. voltage impressed across its `terminals depending as to instantaneous polarity and magnitude also on the function of the potentiometer. In the manifold air pressure servo the potentiometer 31 serves as -an answer card and provides an answer signal at Iits slider contact 32 which is fed back over line l40 to the servo amplifier 28.

As has been stated operation of the right and left turbine r.p.m. servos is controlled according to the operation of the turbo control relay 4, control circuits for each servo extending over kcontact arms '41 and 42 of the -relay l4. The right turbine r.p.m. servo Yfor example connects over line 43, contact 41a, line 44, and iine lwith the slider contact 46 of the turbo-boost selector potentiometer 47 when lthe turbo control relay is cle-energized. Potentiometer 47 connects as shown to negative A;C, supply voltage -E at .one `end and fo ground at the other end. A voltage is derived at the slider contact 46 according to the position of the slider contact on the potentiometer card as determined by the position of a simulated turbo-boost selector lever 48 which connects with contact 46 by means of mechanical connections 49. The simulated turbo-boost selector ylever 48 represents the means by which an engineer in the aircraft selects a desired carburetor entrance pressure. The right turbine r.p.m. servo amplifier 50 is accordingly provided with a signal determined by the position of the turbo boost selector lever and the servo assumes a position corresponding to that signal. The right turbo r.p.m. servo 23 includes the potentiometer card 51 which is connected at one end through the. resistor 52 with a voltage signal -l-OAP representing outside air pressure, and -is connected at its other end to ground. The voltage signal -l-OAP may be obtained in a manner shown and described in the copending application of Robert G. Stern and' William H, Dawson, Jr., for Simulated Manifold Pressure System for Aircraft, Serial No. 436,478, filed Juney 14, 1954 and assigned to the same assignee as the present invention (now Patent No. 2,808,658). A slider contact 52 is positioned along the potentiometer card according to the operation of the servo and assuming an intermediate position on the card Vfor the slider contact as determined by the turbo-boost selector lever the voltage derived at the slidercontact is fed over connection 54 and line S5 to the right turbine r.p.m. servo amplifier 50 to provide anl answer signal thereto. Such voltage is also fed over connection 54, line 56, contact 57a and line 58 with the turbo control relay de-energized to provide an input signal to a summing amplifier 59 for deriving a voltage signal representing carburetor lower deck pressure. This is the pressure between the carburetor and the supercharger inlet.

As shown the summing amplifier 59 also connects with the voltage representing outside air pressure over the line 60; also with the slider contact 61 over the line 62, the slider contact 61 being positioned along potentiometer card 63 through mechanical connections 64 according to the operation of the engine air ow servo 26. The position of the engine airflow servo is determined in accordance with the input signals to the servo amplifier 65, such input signals representing quantities determining air iiow as described in a copending application, Serial No. 436,328 filed June 14, 1954 (now Patent No. 2,824,388) by Stern et al., and assigned to the same assignee as the present invention. As shown the potentiometer card 63 connects at one end with ground and at the other end over line 66 with the slider contact 67 of potentiometer card 68, the slider contact 67 being positioned along the card in accordance with the position of a simulated throttle lever 70 which connects with the contact by mechanical connections 69. The card 68 connects as shown at one end to the A.C. voltage E and at the other end to ground. Accordingly, the voltage derived at the slider contact 61 of the air flow servo 26 is dependent upon both air flow and throttle position. The output of the carburetor lower deck pressure summing amplifier 59 is determined according to the derived input signals respectively representing a function of right turbine r.p.m., a function of outside air pressure and a function of throttle position and air flow, and representing carburetor lower deck pressure in summation. The output of the amplifier 59 is fed over the line 71 to one end of the potentiometer card 72 in the engine r.p.m. servo system 27, the other end of the card being connected to ground. A slider contact 73 is operated through mechanical connections 74 by the r.p.m. servo'rto position the slider contact along the card and a voltage is derived at the slider contact which is fed over line 75 to provide an input signal representing manifold air pressure as a function of carburetor lower deck pressure and engine r.p.m. The engine r.p.m.

servo may be controlled according to control voltages fed to the servo amplifier 74', and derived in the manner shown and described in the copending application of Robert Stern Serial No. 305,730 for Simulated Propeller synchronizing and Speed Control filed September 1, 1954 and assigned to the same assignee as the present invention (now Patent 2,788,589). The manifold air pressure servo 25 is positioned according to the input signal from potentiometer 72 and the indicator 39 operated to a position representing manifold air pressure.

AssuminU theturbo supercharger selector lever 1 is moved from the singleposition to the dual position causing the turbo control relay 4 to pick up after a pre-determined time, contacts 41a and 57a open, and contacts 41b and 57b close. By reason of the opening of the contact 57a and closing of contact 5711, right turbine r.p.m. servo 23 is disconnected from the carburetor lower deck pressure amplifier 59 and the left turbine r.p.m. servo 24 is connected thereto. The left turbine r.p.m. servo connects at slider contact 76 over line 77, contact 57b and line 58 with the amplifier 59. At the time the turbo control relay 4 picks up the left turbine r.p.m. servo occupies a position in which the slider contact 76 is at the grounded end of the servo potentiometer card 78 by reason of the input line 79 -to the servo amplifier 80 having been grounded over the contact 42a and line 81. When the turbo control relay 4 picks up input line 79 connects over contact 42h, line 82, and line 45 with the slider contact 46 to provide an input signal to the amplifier 80 causing the servo 24 including the slider contact 76 to be operated to a position depending on such signal. As shown slider contact 16 connects over connection 82 and line 83 with the servo amplifier 80 to provide an answer signal.

It takes time for the left turbine r.p.m. servo including the slider contact 76 to run up from its initial position in which the slider contact is at ground potential to an intermediate position, and at the instant the relay contact 57b closes, the input line 58 to the carburetor lower deck pressure amplifier 59 is connected over the contact 57b line 77, connection 82, and slider contact 76 to ground at the one end of the potentiometer card 78. The output of the amplifier 59 suddenly drops assuming no change in simulated throttle position or in the engine air flow servo, and the input signal to the manifold air pressure servo is also reduced assuming that the engine r.p.m. does not change. The manifold air pressure servo is caused to run down and the manifold air pressure indicator 39 begins lto register a decreasing manifold air pressure. The indicated manifold air pressure continues to drop until the left turbine r.p.m. servo which meanwhile is running up attains a position such that the voltage derived at slider contact 76 is sutiicient to provide a signal to the amplifier 59 causing the manifold air pressure servo to stop running down and start running upward. Thereafter manifold airpressure is increased until the slider contact 76 attains its final position corresponding to a manifold pressure substantially equal in magnitude to the manifold air pressure realized with the turbo-supercharger selector lever in the single position.

The drop occurring in manifold air pressure by reason of the shifting of the turbo-supercharger selector lever from the single to the dual position is shown in the graph of Fig. 2. As shown, the manifold air pressure indication is unaffected for a pre-determined period of time according to the design of the timing relay 3 after shifting the selector lever; however, at the end of such period the manifold air pressure as represented on indicator 39 begins to decrease and continues todecrease until a balance is struck between the left turbine r.p.m. servo and the MAP servo whereupon the manifold air pressure increases and continues to increase until substantially the original man-ifold air pressure is attained.

In shifting from single to dual `operation the right turbine r.p.m. input line 43 to the right turbinel servo amplifier 50 is connected over contact 41b and llne84 to ground causing the servo to run down and pos1t1on the slider contact 52 at the grounded end of potentiometer card 51. When shifting back from dual to single turbosupercharger operation causing the turbo control relay 4 to drop out a pre-determined period of time after operation of the lever 1, contacts 41h and 42b open and contacts 41a and 42a close. Contact 57b opens and contact 57a closes. The input line 43 to the servo amplifier 50 of the right turbo r.p.m. servo is connected once again to the slider contact 46 of potentiometer 47 and the right turbo r.p.m. servo is caused to'run up positioning the contact 52 on the card 51. Upon the release of the turbo control relay 4 the slider 52 is at the grounded end of the card 51 and when contact 57a closes the input line 58 to the amplifier 59 connects with ground over the contact-57a, line 56, connection 54, and slider contact 52. For reasons hereinabove indicated the manifold air pressure servo starts to run down and the indicated MAP on the instrument 39 decreases. The right turbine r.p.m. servo is running up and an increasing signal is derived at the slider contact 52 which eventually stops the MAP servo from running down, and thereafter the MAP servo mns in the opposite direction to increase the indicated MAP to a value substantially corresponding to the indicated manifold air pressure with the turbo-supercharger selector in the dual position. The fiuctuation occurring in manifold pressure upon shifting from dual to single operation substantially corresponds tothe uctuation illustrated in Fig. 2 occasioned by a shift from single to dual operation.

It is to be noted that the right turbine r.p-.m. servo 23 and left turbine r.p.m. servo 24 are not necessarily operated to positions representing the rpm. of the turbines of the right and left turbo-superchargers respectively, but are so named as a matter of convenience. As hereinbefore indicated, the two servos are provided primarily for the purpose of simulating the fluctuation in the manifold air pressure occurring in the aircraft upon a shift in turbo-supercharger operation. The right turbine rpm. servo 23 does however assume positions representing the r.p.m. of the turbine of the right turbosupercharger for single turbo-supercharger operation, whereas the left turbine r.p.m. servo 24 assumes positions representing the r.p.m. of the turbines of righ-t and left turbo-superchargers `for dual turbo-supercharger operation.

As shown the lines 45 and 17 include instructors right turbo fail switch and left turbo fail switch 90 and 91 respectively. The switch 9? is operable by the instructor to simulate a failure of the turbine of the right turbo-supercharger. If the switch 90 is opened with the system functioning to simulate operation of the right turbo-supercharger only the energizing circuit for the right turbine servo amplifier 50 is opened at the switch 9@ causing the servo to run down whereupon the manifold air pressure servo 25 also runs down to a point reflecting a failure of the turbine. If the switch 91 in -line 17 is opened with the system functioning to simulate operation of the right and left turbo-superchargers the relay 4 is released and the energizing circuit for the left turbine r.p.m. servo amplifier 80 is opened at contact 421: causing the left turbine r.p.m. servo 24 to run down to a point representing the condition in which neither turbo-supercharger is operating.

It should be understood that this invention is not limited to specic details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in `the art without departing from the spirit of the invention.

What is claimed is:

l. In ground based training apparatus for aircraft personnel, 'a simulated control positionable in one of two4 positions respectively representing the selection of one or two engine turbo-superchargers for single or dual operation, a timing device operatively connected with the selector control and operable from an initial condition upon the selectorV control being positioned in one of said positions to a nal condition in a predetermined period of time, operable means connected with the timing device tov function when the timing device attains the said final condition, other means operatively connected with said operable means for restoring the timing device to said initial condition upon said operable means functioning, and means for deriving two control quantities representing simulated differences in manifold air pressure incident to single and dual supercharger operation operatively connected with said operable means, and means for simulating manifold air pressure indication arranged to be responsive alternatively to said control quantities to register the effect of shifting the turbo-supercharger control from single to dual operation, and vice versa.

2. In ground based training apparatus for aircraft personnel, a simulated control positionable in one of two positions respectively representing the selection of one or two engine turbo-superchargers for single or dual operation, means for deriving control quantities representing respectively the simulated effect on manifold air pressure of single and dual supercharger operation, means for deriving control quantities representing the simulated effect on manifold air pressure of throttle position, engine r.p.m., outside air pressure and carburetor air ow respectively, servo means for deriving a control quantity representing the simulated manifold air pressure according to the said derived quantities, said means for deriving single and dual operation control quantities including a pair of servos with only one servo effective according to the position of the turbo-supercharger control at any particular time, and means for operating the selected servo from an initial condition upon positioning the control to cause a uctuation in the control quantity representing manifold air pressure corresponding to the fiuctuation in manifold air pressure occuring in actual aircraft upon shifting the turbo-supercharger control.

3. In ground based training apparatus for aircraft personnel, a simulated selector control positionable in one of two positions respectively representing the selection of one or two engine superchargers for single or dual operation; means for deriving control quantities representing the simulated effects of engine conditions on engine manifold air pressure, means for deriving other control quantities representing simulated effects of single and dual operation on manifold air pressure, servo means controlled according to said derived quantities, an indicator operatively connected to the servo means for registering simulated manifold air pressure, said other control quantity deriving means including a pair of servos operatively connected with the simulated selector control such that operation of one servo is initiated and the other discontinued upon positioning the control in one of the two positions, selection of the servos depending upon the position in which the control is disposed, means for operatively connecting each servo when set into operation to the manifold air pressure servo means and disconnecting the other servo therefrom, operation of one or the other servos of the pair from an initial condition causing a fluctuation in indicated manifold air pressure corresponding to the fluctuation occurring in actual aircraft upon shifting the turbo-supercharger control.

4. In ground based training apparatus for aircraft personnel, a simulated selector control positionable in one of two positions respectively representing the selection of one or two engine turbo-superchargers forsingle or dual operation, a timing device operatively connected with the selector control and operable from an initial condition upon the selector control being positioned in one of said positions to a nal condition in a predetermined 9. period of time, transfer means connected with the timing device to kfunction when the timing device attains the said final condition, other means operatively connected with said transfer means for restoring the timing device to said initial condition upon said transfer means functioning, means for deriving control quantities representing simulated effects of engine conditions and single and dual supercharger operation on engine manifold air pressure, servo means controlled according to said derived quantities, an indicator operatively connected to the servo means for registering simulated manifold air pressure, said control quantity deriving means including a pair of servos operatively connected with the said transfer means such that operation of one servo is initiated and the other discontinued upon positioning the selector control in one of the two positions, selection of the servos depending upon the position in which the selector control is disposed, means including the said transfer means for operatively connecting each servo when set in operation to the manifold air pressure servo means and disconnecting the other servo therefrom, operation of one or the other servos of the pair from an initial condition causing a fiuctuation in indicated manifold air pressure corresponding to the fluctuation occurring in actual aircraft upon shifting the turbo-supercharger control.

5. In trainingv apparatus for aircraft personnel, means for simulating the effects of single and dual engine supercharger operation on manifold air pressure comprising means representing a supercharger selector operable between single and dual positions, means for indicating manifold air pressure in accordance with simulated engine r.p.m. and power condition, alternate means for representing respectively simulated effects of single and dual supercharger operation on manifold air pressure, transfer means operable according to desired single or dual operationfor selecting one of said alternate means for modifying the operation of said manifold air pressure indicating means, and timing means responsive to the initial operation of said selector means from single to dual position, and vice versa, for delaying the operation of said transfer means to simulate characteristic change in indicated manifold air pressure incident to shifting of the supercharger selector control.

6. In training apparatus for aircraft personnel, means for simulating the effects of single and dual engine supercharger operation on manifold air pressure comprising means representing a supercharger selector operable between single and dual positions, means representing a turbo-boost selector for deriving a control quantity according to desired supercharger pressure, means for indicating manifold air pressure in accordance with simulated engine r.p.m. and power conditions, alternate means for representing respectively simulated effects of single and dual supercharger operation on the simulated manifold air pressure adapted to be energized by said control quantity, relay means responsive to said selector means and operable according to desired single or dual operation for selectively connecting one of said alternate means so as to modify the operation of said manifold air pressure indicating means, and timing means responl sive to the initial operation of said selector means from single to dual position, and vice versa, for delaying the operation of said relay means to simulate characteristic change in indicated manifold air pressure incident to shifting of the supercharger selector control.

7. In training apparatus for aircraft personnel, means for simulating the effects of single and dual engine supercharger operation on manifold air pressure comprising means representing a supercharger selector operable between single and dual positions, means for indicating manifold air pressure in accordance with simulated engine r.p.m. and power conditions, alternate servo mechanisms adapted to be energized according to desired supercharger pressure for representing respectively simulated effects of single and dual supercharger operation on manifold air' pressure, transfer means operabe according to desired single or dual operation for selectively connecting one or the other of said servo mechanisms to said manifold air pressure indicating means for modifying the operation thereof, and` timing means responsive to the initial operation of Ysaid selector means from single to dual posit'on, and vice versa, for, delaying the operation of said transfer means, said servo mechanisms being of the selfpositioning type so as to be operable upon energization from the zero position thereof to a position corresponding to said desired supercharger pressure for, in combination with said timing means, controlling said indicating means and simulating characteristic change in indicated manifold air pressure incident to shifting of the supercharger selector control.

8. In combination, double throw selector means positionable from a first to a second position and vice versa and having a first set of coacting contacts; a normally deenergized timing relay having a movable and a coacting normally open contact; relatively rapidly responsive double throw relay means having a second set of coacting contacts that are in the steady state in positions corresponding to those of said selector means depending on whether said relay means is respectively deenergized and energized; hold circuit means for maintaining said relay means energized upon initial energization thereof; means including said contact sets in the two possible combinations of none-corresponding positions due to change in position of said selector means for energizing said timing relay to effect closure of said normally open and movable contacts upon lapse of a predetermined period of time; means including said first contact set responsive to said closure for initially energizing said relay means when said selector means is then in its second position and for deenergizing said relay means when said selector means is then in its first position thereby to restore said position correspondence, to deenergize said timing relay once more, and to reopen said movable and normally open contacts, in readiness for another timing operation in response to operation of the selector means, whereby the time delay to attainment of said correspondence is substantially the same in the case of switching of said selector means from its first to its second position as in the reverse case.

9. In combination, double throw selector means positionable from a first to a second position and vice versa and having a first set of coacting contacts; a timing relay normally in one of the energized and deenergized circuit states and having a movable and a coacting stationary contact that is normally in one of the open and closed states relative to said movable contact; relatively rapidly responsive double throw relay means having a second set of coacting contacts that are in the steady state in positions corresponding to those of said selector means depending on whether said relay means is respectively deenergized and energized; hold circuit means for maintaining said relay means energized upon initial encrgization thereof; means including said contact sets in the two possible combinations of non-corresponding positions due to change in position of said selector means for transferring said timing relay from its normal circuit state to the other of its said two states to effect transfer, relative to said stationary contact, of said movable contact from its normal state to the other of its said two states upon lapse of a predetermined period of time; means including said first contact set responsive to said transfer of states of said movable contact for initially energizing said relay means when said selector means is then in its second position and for deenergizing said relay means when said selector means is then in its first position thereby to restore said position correspondence, to retransfer said timing relay to its normal circuit state once more,

and to retransfer said movable contact to its normal state in readiness for another timing operation in response to operation of the selector means, whereby the time delay 1l 12 to attainment of said cgrrespondence is substantially the; 2,499,597 Lukacs .Y Y Mar. 7, 1950 same in the Case 0i swthng of said sel'etor means from' 2,506,949 Burelbae-h, et a1. May 9, 1950 its first to its second position as inthe reverse case..

References cima in the fue of this pam-f I UNITED STATES' 1 ATE1-ITS` f 2,057,384 Lamb 0a. 13,y .193e 

